Greater efficacy of SPF 100+ sunscreen compared with SPF 50+ in sunburn prevention during 5 consecutive days of sunlight exposure: A randomized, double-blind clinical trial

J Am Acad Dermatol. 2020 Apr;82(4):869-877. doi: 10.1016/j.jaad.2019.09.018. Epub 2019 Sep 19.


Background: Beach vacations are high-risk settings for overexposure to ultraviolet radiation.

Objective: To compare the sunburn protective efficacy of SPF 50+ and SPF 100+ sunscreens under actual use at the beach.

Methods: A prospective, randomized, double-blind, single-center, split-body/face study of 55 healthy individuals. Each participant applied both sunscreens to randomized sides of the face/body for up to 5 consecutive days. Blinded clinical evaluation of erythema by a single grader and objective instrumental assessments, colorimetry, and diffuse reflectance spectroscopy were performed the morning after each sun exposure.

Results: After 5 days, 31 (56%) participants had more sunburn on the SPF 50+ side compared to 4 (7%) on the SPF 100+ side. Overall, mean erythema intensity showed statistically significantly less erythema on the SPF 100+ side compared with the SPF 50+ side. The first observation of sunburn exclusively on the SPF 50+ side occurred after 1 day of sun exposure, whereas that for SPF 100+ occurred after 3 days of sun exposure.

Limitations: Only initial sunscreen application was monitored, only 1 participant with skin phototype I was recruited, and participants were recruited from a local beach area.

Conclusion: SPF 100+ was significantly more effective in protecting against ultraviolet radiation-induced erythema and sunburn than SPF 50+ in actual use in a beach vacation setting.

Keywords: SPF; beach; clinical research; general dermatology; medical dermatology; prevention; sunlight; sunscreen; sun protection factor; vacation.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adolescent
  • Adult
  • Colorimetry
  • Double-Blind Method
  • Female
  • Humans
  • Male
  • Middle Aged
  • Prospective Studies
  • Spectrum Analysis
  • Sun Protection Factor*
  • Sunburn / prevention & control*
  • Sunscreening Agents / administration & dosage*
  • Sunscreening Agents / therapeutic use
  • Young Adult


  • Sunscreening Agents